Investigation of Physicochemical Properties of Tapioca Starch–Methyl Myristate Complexes

Abstract

Complexation can be utilized to modify starch properties. In this study, tapioca starch–methyl myristate (SM) complexes are prepared by mixing tapioca starch and methyl myristate (MM) in water at 90 °C. The MM amount is varied at 1%–10% w/w to study its effects on the complexes’ physicochemical properties, which are characterized using spectroscopic, thermal, crystallinity, particle size, and microscopic analyses. The complexes are stable crystalline materials, as iodine cannot replace complexed MM. In water, these complexes aggregate to form two different sizes of 29.5–162.7 nm (23%–58% population) and 711.2–7086.7 nm (42%–77% population), which melt at 90–95 °C. Solid complexes form porous morphologies, which start degrading at 260.3–263.4 °C, indicating high thermal stability. An in vitro digestibility study using α-amylase shows that the higher the MM amount is, the slower the starch degradation. At 120 min digestion time, the complexes produce 11%–16% lower reducing sugar than native starch (S). This shows that starch complexation with MM complexes can produce starch materials with slower digestibility. For the kinetic analysis, the Weibull model fits better than the exponential model for analyzing the digestion kinetics of SM complexes by the α-amylase enzyme.